Patent GB-1389746-A (GB)
Title: Machines for carrying out an operation on a web
IPC: B65B51/00
Filed: 1972-08-01
Abstract: 1389746 Seaming non-metallic sheet material FMC CORP 1 Aug 1972 [23 Aug 1971] 35838/72 Heading B5K [Also in Divisions B8 and H5] A device for transversely welding a weldable web comprises a welding tool which participates in the movement of the web along a portion of the path thereof. The device forms a transverse sealing and severing head 10, Fig. 1, in a continuous wrapping machine 12 in which articles A fed from a conveyer 16 are entubed in a longitudinally sealed polyethylene or laminated film web W. Individual wrapped packages P are discharged by a conveyer 26. The head 10 comprises sealing and severing jaws 50, 52, Fig. 2, driven by shafts 54, 44, respectively, the shaft 44 being driven from a main drive shaft 32 through a train of helical gears 34, 36, 38, 42 and a barrel cam 46 and the shaft 54 being driven by meshing gears 59, 60. Cam rollers 78, Fig. 5, are mounted on the shafts 54, 44 by bars 76 and engage in cam grooves 70, 74 in blocks 68, 72 secured to bearing blocks 66 retained by vertical slides 62, 64, Fig. 1. Drive members 80, 85 straddle the shafts 54, 55, respectively, and connect the jaws 50, 52 thereto. Electrical power is fed to the shaft 54, Fig. 2, by a slip ring unit 86 having one conductor 88 grounded to the shaft and a second conductor 90 connected to a conductor rod 92 which extends through insulator bushings in an axial bore in the shaft 54 and has a slotted inner end, Fig. 4A (not shown), which intersects a transverse aperture in the shaft 54. A nylon sleeve 94, Fig. 5, is mounted in this aperture and retains a split nylon bushing 96. The split end of the rod 92 extends through the members 94, 96 and grips a flat conductor 98, e.g. of beryllium copper, curved towards and clamped by bolts (103), Fig. 4 (not shown), to the rod 76. A sealing and severing wire 104, e.g. of nickelchromium alloy, extends between one bolt (103) and a bolt (103a) clamping a second conductor 98a to the rod 76. The bolt (103) is electrically isolated from the rod 76 whereas the bolt (103a) is not and the conductor 89a is electrically grounded to the shaft 54. The wire 104 is electrically insulated from the jaw 50 by a bar 124 and operates against a silicon rubber anvil 126 on the jaw 52. Silicon rubber presser bars 120 are mounted on the jaw 50 to engage metal ribs 122 on the jaw 52 during sealing. In operation, the jaws 50, 52 begin to close, Fig. 7 (not shown), and pinch the web T near the trailing end of the leading article therein which is supported by the conveyer 26 and a rotating support 130 connected to the shaft 44 by a bar 132. As the jaws 50, 52 approach the position of Fig. 5, the barrel cam 46 provides a velocity correction to accelerate the shafts 44, 54 which are decelerated when the jaws travel beyond their dead centre position. By this arrangement, the jaws 50, 52 have a constant linear velocity which is the same as the web velocity during the entire period of web engagement which is for at least 40 degrees of each 360 degrees sealing cycle. In a modification, Fig. 6, two jaws 50, 110 are provided on the shaft 54 and two jaws 52, 111 on the shaft 44. A flat conductor 112 extends through the shaft 54 to serve both jaws 50, 110.